Air-suspended vehicles with a level control system customarily have a compressed air store, a level control valve for the automatic, load-dependent adjustment of the vehicle level, air spring bellows assigned to at least one vehicle axle, and a control valve device for manually adjusting the level of the vehicle body bypassing the level control valve. A control valve device of this type generally has a shut-off valve installed with the air spring bellows in a line connection of the level control valve, and an inlet valve and an outlet valve for manually admitting air to and discharging air from the air spring bellows.
In other words, in addition to the level control valve which adjusts the level of a trailer platform or of a trailer frame to a constant value in a known manner, air suspension devices having air spring bellows are provided with a manually actuatable control valve device by which an operator, bypassing the level control valve, can set a desired level position of the trailer platform or of the vehicle body. For this purpose, the level control valve unit is set manually into the positions “lift”, “lower” or “stop”. For this purpose, the control valve device has a control element generally in the form of a manual actuation arrangement with which, for example, a level position desirable for loading the vehicle on a loading ramp can be set. Furthermore, there has to be a “drive” position in which the level control valve becomes effective again.
A control valve device of the type in question is discussed, for example, in German patent document DE 41 20 824 C1. The control valve device has a selector shaft which, by pressurization of a control piston, can be displaced axially between the stop and drive positions and, by rotation out of the stop position, actuates the inlet valve for the lifting or the outlet valve for the lowering. The inlet valve, the outlet valve and the shut-off valve are arranged in different axial planes of the selector shaft. By pressurization of the control piston with compressed air, the control valve device can be transferred into the drive position. The spring arrangement returns the control element in the form of a hand lever into the stop position.